This invention relates to new and useful improvements in priority flow control valves and consists of an automatic switching valve which is mounted between a pair of sources of gas or liquid under pressure in which the pressure of at least one of said sources fluctuates and which automatically switches the valve to supply the gas or liquid that is under the higher pressure. However, if the pressure is equal on both sides, both valves will open simultaneously if the pressure is above the cracking pressure.
For example, the valve could be mounted between two gas sources such a propane gas and natural gas that supply a pump jack motor in an oil well. The regulator on the propane tank would be set at the minimum pressure required to operate the system but propane would only be consumed when there was not enough natural gas present.
This supply of natural gas in oil well pumping normally is available from the oil well that is being pumped and of course the use of this natural gas is of considerable benefit to the oil industry as it is available free of charge from the oil well.
However, such a source does fluctuate in pressure and quantity hence the necessity for a standby tank of propane under pressure which of course is far more expensive than using the free source of natural gas from the oil well.
Under this particular condition, only one source would be fluctuating in pressure, namely, the source of natural gas from the oil well whereas the propane, providing sufficient supply is maintained, is at a relatively constant pressure.
Another example might be a remote source of natural gas from another well together with the natural gas from the well being pumped. Under this condition, both sources might well fluctuate so that the valve operates always to supply gas from the source of higher pressure.